A two-stroke engine is known having divergent pistons, the inventor of which is the applicant of the present application, which piston mechanism comprises a cylinder in which pistons are arranged opposite each other, forming working chambers, the pistons being joined by two pairs of rods in two groups having an opposite direction of movement. Pistons of one of the directions of movement are firmly attached on each pair of rods and spaced from one another, alternating with pistons of the opposite direction of movement. The rods of one group of pistons run through the pistons of the other group and vice versa. These rods cooperate with three crankpins of a crankshaft via links. Two outer rods for the pistons of one direction of movement are joined with two outer crankpins, while two inner rods for the pistons of the opposite direction of movement are joined with a middle crankpin (see German application DE 3237858, Class F 01B 3/00, F 04B 27/00, 1984 r.).
The advantage of said piston mechanism lies in its ability to increase the effectiveness of its work by a provision of working chambers from both sides of each piston, which allows a twofold increase of the effective capacity, and also by the connection of the rods with three crankpins of the crankshaft, which allows the pistons of the same direction to work synchronized and parallel to one another.
However, a major shortcoming of this design is the problem of sealing the rods in the regions where they run through the pistons of the opposite direction of movement. A lack of effective sealing results in leakage of the working chambers and decreases the reliability of the piston mechanism as a whole. Moreover the cross movement of the rods and pistons taking place in this arrangement increases the wear of the cylinder walls and disrupts the evenness of the piston movement, which is disadvantageous for the working characteristics of the piston mechanism.
A two-stroke engine having divergent pistons is known, the inventor of which is identical with the applicant of the present invention, wherein two opposite cylinders are arranged along a common axis. The piston mechanism of each cylinder comprises two divergent pistons acting on a common crankshaft directly by power elements (connecting rods). The crankshaft comprises two basis pins and three crankpins, the two pistons adjacent to the crankshaft acting on the middle crankpin and the two pistons spaced from the crankshaft acting on the two outer ones. The pistons of the same direction of movement adjacent to the crankshaft are firmly attached to one another by a hinge guiding a slide bar joined to the middle crankpin. The pistons spaced from the crankshaft are joined to the outer crankpins by links (see German patent DE 4135386, Class F 02B 75/28, 75/32, 1992 r.).
The advantage of this technical solution is the replacement of rods by power elements—connecting rods and a slide bar directly acting on the crankshaft and outside the borders of the working cavity of the cylinder. Thus it becomes possible to house a second piston in each cylinder. This exchange of the piston rods of one direction in favour of connecting rods makes it possible to seal the joint of the cylinder-piston system. The suggested two-stroke engine is characterised by its compactness, low weight of the construction, the possibility to use multiple cylinders and low manufacturing costs.
The disadvantage of said two-stroke engine having divergent pistons is its marked friction of the hinge, which necessitates a frequent exchange.
A two-stroke engine with divergent pistons is known having a piston mechanism comprising opposite cylinders with a stepped inner cavity having inlet and outlet openings and two pistons meeting each other in each of them, and a crankshaft with three crankpins. Both outer crankpins are joined with a sliding sleeve (an outer connecting member) by a link, wherein the sliding sleeve slides through the cylinder body like on a guide rail and is joined with the pistons spaced from the crankshaft by a synchronised group of connecting rods. These connecting rods are arranged so that they can move back and forth in guiding channels arranged in the cylinder body parallel to its axis. The middle crankpin is joined to the pistons adjacent to the crankshaft through at least one link and an internal connecting member. The internal connecting member is disposed in the cavity of the cylinder and is integral with the pistons with apertures for the crankshaft to pass through and move freely (see patent DE 19503444, F 02B 75/32, F 02B 25/10, 1998).
The advantage of said known piston mechanism is that the piston rods of one direction of movement are replaced by a group of connecting rods moving in synchronicity together with one connecting member in one case, and the connection of the pistons of the opposite direction of movement directly with the other connecting member, allowing a linear synchronous movement of the pistons in both cylinders in another case. By linking the connecting members and the crankshaft, the wear of the connecting hinge mechanism and the basic bearings lessens. In any position, the crankshaft is only loaded with the differing force of both resultants, the periodically activated forces of gas and mass on the inner and outer crankpins of the crankshaft. This positive effect multiplies as the number of revolutions of the engine increases.
A disadvantage of said technical solution lies in the different types of the outer and inner connecting members, which makes the design more complex and increases the dimensions and the weight of the mechanism while the kinetic connection of the pistons with the connecting members is difficult. The construction must be manufactured with great exactness. The problem of arranging more than two diverging pistons in one cylinder remains unsolved to date.